Dental casting alloy



lPateatefi Apr. l8, 1%39 unrrso STATES FIQE No Drawing. Application lluly 6, 193%, Serial No. 217321 2 Claims, (Cl. '35- 17l.)

This invention relates to metallurgy and more particularly to an alloy suitable for use in the manufacture of cast dentures and the like.

In the manufacture of metallic dentures the alloy composition employed must be stainless and non-corrosive towards various acid and alkaline reagents present in the mouth or in various foods or liquids. The alloy also must be wear-resistant an" the alloy must be variable as to percentages oi the several constituents to a sufiicient extent to permit the obtainance of degrees of strength and. flexibility permitting its use under a wide variety of service conditions. Moreover, the alloy composition must be adapted to being readily cast iree irom blow holes; voids and from slag and onirle inclusions, in a variety of irregular shapes configurations cormnon to dentures with a minimum of material loss and with a minimum of material surplus, by the ordinary methods practicecl in the art.

The present-invention aims to provide an alloy pterl to meet these many conditions sncl iurt er aims to provide a denture comprised of the alloy.

rhe olloy composition of the comprises a base consisting of in such present invention nickel and cobalt relative proportions as to give the restrength, toughness and Wear-resistant i chromium in suiilcient ase stainless and corrosion e i may incorporate roar o such amounts as w etely rleoxiriize the alloy and e deleterious effect of any sci or or cartoon or sent in the base and may also incorporate a percentage oi molybdenum or tungsten or looth in such an amount as will augment the normal strength orrigidity oi the case. Into the hose or into the base improved by additions of one or more of the metals manganese, silicon, molybdenum and tungsten, I incorporate a sufieient percentage oi boron as will effectively protect the alloy constituents from oxidation during subsequent re rnelting and casting to form dentures.

in the manufacture of dentures it is customary in the art to melt the alloy in an open crucible by impinging thereon the open flame of an 02. acetylene or city-hydrogen blow torch. When fully molten the alloy is centrifugally cast into a mold wherein relatively rapid solidification occurs. Heretolore in the art it .has been dificult to manufacture cast dentures of metals other than the noble metals in this manner one to the loot that it is impractical to employ a protective slag over the metal during the melting and casting operation as the slag, when used, also entered the mold and was entrapped by the rapidly solidifying metal, causing blow holes, voicls and'the like. When, however, a protective slag was not userl during the melting operation excessive oxielation or the metal constituents occurred and. voicls caused by oxioe and gas occlusions are obtaineel. This circumstance has greatly limited the use and adaptation of chromium-containing alloys, particularly in the forming or" cast clentures, clue to the fact that when molten or curing melting the chromium content of such alloys rapirlly oxidise to form rlifilcultly fusible oxide com-= pounds even though the alloy has been covered. or protected by readily fusible slag materials.

have found that the most efiective way to prevent the (ini ation of the chromium in chromi urn-containing alloys is to incorporate in the alloy an alloy constituent which is more readily oxirlizahle than the chromium and which on oxielation forms a relatively low melting slag oper= ating to protect the alloy from direct contact with oxidizing agents. Boron is the only alloy constituent of which 1 am aware that will accompiish this rlesirecl result.

The amoimt oi heron I may incorporate in the alloy composition oi the present invention may vary tvizlely Without eepaz have success iuliy enrol high as race /.5, all e expert s concli= tions at boron content of less their 113% proha' loly can be employed "out antler the ordinary manipulating conditions oi melting anti casting nreier to have present in my alloy about boron, as this amount portraits of repeated rernelting without detrimental results to the alloy. The excess oorori cloes not appear to he vdeleterious in the alloy but to the contrary appears to increase the fluidity oi the alloy when molten and the ease with which it may be cast, and cast dentures of my alloy containing 5% or more boron appear to be more sharply defined than those containing 1 or 2% boron. This amount of boron, moreover, appears to beneficially afiect the physical proper ties of the alloy, making it of finer grain struc ture and improving its hardness and luster.

In my alloy composition I prefer to limit any hair conmnt to less than 1.00%. Iron in amounts greater than this, W" 1e being of advantage in some respects, such as giving arlried strength and ductility, sistance properties and require added chromium to counteract the same. For this reason, I prefor to limit my invention to a niclrel=cobalt-chrocletrimentally cfiect the corrosion re=' tungsten content I tent may vary from mainder of the aloy consisting of boron in amounts upto 10% but preferably about 5%and manganese 1 to 2% .erties in the alloy. Where molybdenum 2 q niium' base with 1.0.. less than 1.0%..111 um base alloy the chromium content may vary in amounts from 5% to 30% and the cobalt .con-

nickel except or silicon up to 1% or both. I flnd it preferable to increase the cobalt with decrease in chromium within the rangesspecifled although this relation is not empirical but solely for the purpose of maintaining relatively constant corrosion resistance propor tu'ng; sten or both are added to-the alloy as stiflening constituents, I prefer to add these. elements as.

. replacements for part of the cobalt and in this pose use in the casting of dentures have the following analyses:

s I II III Percent Percent Percent 0 l. 0 max. 1. 0 max. 1. 0 1. 0 i. 0 5.0 5. 0 5. 0 0 l. 0 l. 0 max. 7

Alloys suitable for the same purpose but stronger and more suitable similar to composition No. I but contain molyb-. denum 2-8% with the cobalt reduced a corresponding amount, or tungsten 1-4% with the cobalt reduced a corresponding amount.

'Where a softer alloy is desired, as in the form ing of pins, bars and the like which subsequently are to be bent to-shape, I increase the nickel to about 50% and lower the cobalt a corresponding amount. The boron content of this alloy operates to facilitate the subsequent weld attachment of these pins or bars to a cast denture and even permits the casting of the denture directly onto the pin orbar as heretofore practiced in the art with other metals.

In the manufacture of the alloy composition of the present invention I prefer to separately 10 to 50%, with the re- 7 the metal metal is cast centrifugally into the denture mold for bridge work are form a'cobalt-nickel alloy, a chromium-nickel alloy, and a nickel-boron alloy or a nickel-chromium-boron alloy either of which alloys may contain manganese in such amounts as is necessary to effectively neutralize any sulfur present in the alloys. These alloys preferably should be substantially free from carbon and from iron.

I'then mix the various alloys together, preferably in small sized pieces, in such relative atively small diameter rods which after solidifl-. I

.or broken into relatively small cation may be cut ably add themin the form of nickel alloys of these metals.

- In the forming ofa denture from this alloy,'

a sufficient amount of these small sizedjpiece's of rod is placed in an open crucible and is melted by. the direct application thereon of the oxyacetylene or oxy-liydrogen flame and as soon as becomes molten'and fluid as heretofore practiced in the'art. The thus formed cast denture will be substantially free from blow holes, voids, or of oxide and slag inclusions. the meltingprior to casting fo such a fluid slag that on entering the mold during casting the same .,does not interfere with. the entrance of the molten metal into the finest crevices of the mold, and a clearly defined sound, casting will be obtained.

From the above description of the present invention, it will be apparent that the same may be widely varied as to alloy departure from; the invention and all such modiflcations and variations. are contemplatedas may fall within the scope of the following claims.

What I claim is 1. An alloy suitable for use in the manufacture of substantially souncfnon-oxidized cast denture and the like, said alloy consisting of cobalt, 10 .50%; chromium 540%; boron 1-10%, remainder nickel. v

. 2. A casting alloy for dentures comprising chromium -30%, cobalt 10-50%, boronl-10% the amount of said ing is obtained.

CO JOEL'GROSSMAN.

composition without the fmolten so Any boron which is oxidized during 

